The subject matter disclosed herein relates to the art of rotary wing aircraft and, more specifically, to a rotor control system for a rotary wing aircraft.
Control of rotary-wing aircraft is affected by rotor blade pitch variations. The rotor blades are controlled individually (cyclic control) and collectively (collective control). Main rotor pitch control is typically achieved through a swashplate assembly that transfers motion of non-rotating control members to rotating control members. The swashplate assembly is typically concentrically mounted about a rotor shaft. A typical swashplate assembly includes two rings connected by a series of bearings. One ring is mounted to the aircraft (stationary) and another ring is mounted to a hub portion of the rotor shaft (rotating). Movements in the stationary ring are transferred to the rotating ring to control blade pitch.
Rotary-wing aircraft having dual or counter-rotating rotor blade systems require both an upper rotor control system and a lower rotor control system. The lower rotor control system utilizes a conventional swashplate assembly mounted about a lower control rotor shaft. The upper rotor control system is typically more complex and utilizes an upper rotor control shaft mounted through the lower rotor shaft. The upper rotor control system includes an upper rotor swashplate assembly, a motion multiplier, and long control rods located inside the upper rotor control shaft. The long control rods are prone to buckling and thus must be sized accordingly adding weight to the control system. Sizing of the control rods to fit in the upper rotor control shaft can be difficult, however, since it is also advantageous to reduce the diameter to the upper rotor control shaft to reduce system weight.